The present disclosure relates to a battery comprising a battery cell, preferably a lithium-ion battery cell, in which an external and a battery-cell-internal temperature sensor are arranged.
It is becoming apparent that in the future battery systems will be used to an ever greater extent both in stationary applications and in vehicles such as hybrid and electric vehicles. In particular, batteries are increasingly being used as traction batteries for use in hybrid and electric vehicles and thus for supplying electric drives. FIG. 1 shows such a battery 200 from the prior art. It comprises a battery cell 100 having a housing 70 and a cell core comprising an electrode arrangement 10 for generating energy.
Mathematical battery models are used for the operation of the battery 200. In this case, however, internal resistances and time constants of the dynamic battery cell behavior under load are greatly dependent on the temperature in the cell core in which the chemical reactions take place. On account of load-governed production of heat, the temperature in the cell core can change rapidly.
According to the prior art, the temperature measurement on battery cells takes place by means of temperature sensors that are usually fitted on the housing. In this regard, DE 199 61 311 A1 discloses a temperature sensor that is fixed to the battery from outside by means of a battery terminal. The temperature-dependent battery model parameters are then mapped onto the housing temperature offline or online. However, the exterior temperature of the housing does not correspond to the core temperature in the interior of the housing at the electrode arrangement, nor is it unambiguously linked thereto. Consequently, a change in the core temperature is measured in a delayed fashion or is not measured at all on the battery cell housing owing to thermal contact resistances within the cell and toward the outside.
The inaccurate detection of the present temperature in the cell core leads, as a consequence, to inaccuracies in temperature-dependent battery models of the operating state of the battery. The battery models can be used both in the battery control unit for monitoring and controlling the operation of the battery and outside the battery in an offline simulation.
DE 100 56 972 A1 discloses a battery cell in which sensors for determining the battery temperature are arranged in the housing of a battery cell. The temperature sensors are embodied as temperature detectors and connected to the exterior region of the battery housing via electrical lines. Although the installation of customary measuring probes, containing e.g. an NTC measuring unit of conventional three-dimensional design, in the interior of the battery cell can detect the cell core temperature, it nevertheless influences the evolution of heat and the heat flows in the battery as a result of the detection and evaluation units and the signal lines.
Furthermore, Makinwa and Snoeij (“A CMOS Temperature-to-Frequency Converter With an Inaccuracy of less than +−0.5° C. (3σ) from −40° C. to 105° C”, K. A. A. Makinwa, Martijn F. Snoeij, IEEE Journal of Solid-State Circuits, vol. 41, no. 12, December 2006, pages 2992-2997) disclose a temperature-to-frequency converter that is implemented in a standard CMOS method.
Furthermore, the battery can also contain a cooling system for cooling the battery cells. A further temperature sensor can then be arranged in the cooling system.
According to the prior art, both the temperature sensor on the housing and the temperature sensor in the cooling system can have a high accuracy with regard to their absolute temperature measurement capability, but are sluggish when detecting fast temperature changes within the battery cell owing to the installed position and the heat transfer path. This results in a delayed reproduction of a temperature rise in the interior of the battery cell, particularly in the case of safety-critical—on account of being very fast—temperature rises owing to a short circuit.